mercruiser engine replacement

I just got a boat from a friend for free.The hull and interior are in great shape the outdrive was rebuilt 4yrs ago and was not used much.The engine was replaced at the same time 305 mercruiser.The exhaust manifolds rusted through and leaked water into two cylinders.I have to replace the engine and was wondering if this was something I should attempt my self?Im a great automotive mechanic and was looking at this job and it looks easy.Is it as easy as it looks?Or is there a book someone could reccomend?Thank You for any help you can provide.

Re: mercruiser engine replacement

You can do it. Just make sure ANY parts you use are marine. Many parts are specially sealed for marine use such as: alternators, starters, etc. They're not worried about water getting in them, they're worried about fuel fumes getting in them. I have seen a boat blow up-it was terrifying.<br /><br />The same goes for internal engine parts to some extent. Marine engines are built to have a very flat torque curve. This is usually done by valve timing. Remember, a marine engine does NOT EVER coast. It is under load at all times. You can rebuild the engine yourself, just make sure to set it up as a marine application.<br /><br />By your description, you'll have to replace the exhaust manifolds and elbows. This should run about $400.00 for manifolds and $300.00 for elbows. You want to make sure these are good or you will get to do everything over again. If you do not want to go OEM on these parts, that's OK. Osco makes good ones.<br /><br />The only special tools I can think you will need is an alignment tool to line up the engine with the driveshaft. <br /><br />This sounds like a great project-good luck and Happy Holidays!!

Re: mercruiser engine replacement

Wheels4,<br /><br />I mentioned in my last posting that I had seen a boat explode. We outies are much less likely to have that happen, however SAFETY is paramount. Let me share the story.<br /><br />I was ready to go fishing out of Chalmette, LA in the early eighties. About 50 yards away was a 28-30 ft. Bertram with gas burners that had just refueled. There were two guys aboard.<br />After fueling, the guy behind the wheel hit the ignition key and all hell broke loose.<br />The second guy that was standing in the cockpit on the engine hatches was blown about 2o feet into the air followed by a huge mushroom fireball. He landed in the water about 30 feet from the boat. Believe it or not he was still conscious and commenced swimming to shore. All he suffered was a broken ankle and was scared out of his wits.<br /><br />The guy at the controls was blown forward into the dash of the boat and suffered some nasty facial cuts. The only thing that saved him was the bulkhead betweeen the cockpit and the pilothouse. He to, miraculously, was still conscious and jumped out and swam before the whole thing burst into flames.<br />The boat basically burned to the waterline.<br /><br />As I mentioned, I was a good fifty yards away and I was nearly thrown off the dock. The heat was incredible.<br /><br />Just a word to the wise-be careful out there-gasoline and particularly its fumes are deadly.<br /><br />I don't want to scare you innies, just make sure you check those fuel connections often and ALWAYS vent those bilges thoroughly.

Re: mercruiser engine replacement

Thank You for the reply.The parts I will be using are all marine.It seems they replaced everything accept the exhaust manifolds.Even the power steering pump looks new.I dont know why they would cheap out on the manifolds after spending all that money on the engine and outdrive???I would like to put my 327 short block in.Would this be o.k. if I used a marine cam?I know this is a good shortblock but would the outdrive handle the extra power?I appreciate your help and have also seen the aftermath of an explosion the opperator of that boat was not as lucky.Happy Holidays.

Re: mercruiser engine replacement

Wheels4,<br /><br />Alot depends on your outdrive. If it is an Alpha or Alpha 1, you'll be OK. Bravo? or TRS?-no sweat. Don't go crazy on the mod's. The Alpha drives can handle about 300 ponies. The types 1 and 2 before them struggled with 260.<br /><br />The 327 makes a good marinization. Use the cam profiles for the old marine versions.

Re: mercruiser engine replacement

Wheels4, The 327 will work as far as the bolt hole alignment. The horsepower will not make that big a difference,but the engine will have to have a marine distributor. The springs in a marine dist. advance different than an automotive due to the torque curve. The engine will have to have brass freeze plugs, the 327 heads are pre unleaded, So heads will need to have new seats. Carberator has to be marine with flame arrestor, marine carb has a different vent system to keep from loosing gas in ruff water. Cam can be a low end torque cam for truck or camper apps. Great deal of work!!Are you sure the other engine is shot? Beat bet is hone cyc. and rebuild. Rick Luck seems to follow those who don't rely on it

Re: mercruiser engine replacement

Wheels, this is a very do-able project for someone who wrenches on cars for a living.....But this will be the LAST time you call that boat free!

Re: mercruiser engine replacement

Thank You for all the replies.djohns19 the outdrive is I believe a alpha1 that was rebuilt in 98 with only one season of use.Loper,i will be using the intake carb and distributor that are in the boat now.They are all in great shape along with the water pump alternator etc.Like i said all this stuff is like new.I already have the 327 short block that was in my camaro cyl. walls are in great shape.Also have heads with hardened seats and bronze guides 9.1 compression.I was worried about the exrta power about 300.Seems like this will work though.Last but not leastODDD1 youre not kidding about this being the last time I call this boat free my girlfriend already had to do without a couple of CHRISTMAS gifts this year.But its all about me!me!me!HAPPY HOLIDAYS!

Re: mercruiser engine replacement

Wheels4, sounds like a fun project! The best part will be taking your friend for a spin in his old boat. I have a buddy who bought a boat and changed from a tired 305 to a warmed-over 350, and when the previous owner went on a cruise, he almost cried. What a difference 75+ horsepower makes!

Re: mercruiser engine replacement

Wheels 4, remember to use a marine cylinderhead gasket. Theese have stainless reinforcement, to resist saltwater.<br /><br />It is a funny job, i tried it on a volvo gasoline 170 engine. Everything worked out fine.<br /><br />Good luck.

Re: mercruiser engine replacement

Wheels4,<br />You're on your way. Be careful with those extra ponies. Do everything-marine.<br /><br />You'll have a VERY nice set-up.<br /><br />Green with envy!!!

Re: mercruiser engine replacement

Thanks for all the replies but I have one more question.This engine seems to be fresh water cooled.There is a large tank on front that seems to have antifreeze in it.If so should i still use brass freeze plugs?Also what manuel would you recommend I pick up?The more I read the more I want to get this thing going.I will not skimp on parts though.Ive been building a 69camaro for three years so I know these things take time.The great thing is this boat only needs an engine.The car needs everything but an engine.<br /> HAPPY HOLIDAYS!!!

Re: mercruiser engine replacement

YES EVERYTHING SHOULD BE BRASS OR STAINLESS.<br />REX A. HUBBLE

Re: mercruiser engine replacement

With that closed cooling system its going to be ALOT CHEAPER to rebuild the engine you got. You change engine..Be careful.. Brackets will be different and you may not find the manafolds and risers that you need to fit the boat. <br /><br />By the way whats wrong with the engine you got??

Re: mercruiser engine replacement

also remember to take the oil baffle plate off the old motor and put it on the 327 i once put a 400 small block in my boat without it ran great for a week really fast till all the oil splashin around tore up the insides ended up puttin a rod right through the block best thing to do is make sure everything is marine regular car aprts dont cut it in a boat they dont hold up to the wet conditions have fun and be safe

Re: mercruiser engine replacement

That merc probably has much better components than the one you want to install. Things of importance, like connecting rods, pistons. They are very different from the street application we all have in our pickups and cars. Before you install a new one you should consider a rebiuld instead. Just hold a car piston next to the one out of that merc, you'll see what i mean. A stock rod will never hold up in a boat due to the constant high rpm's. Be carefull!

Re: mercruiser engine replacement

The problem this engine had was both manifolds rusted through(pin holes)water leaked into #3,5,4,and6 cylinders.It will not turn over rusted pretty bad.I was going to just pull the heads to get a good look but when I got the manifolds off I could see the cylinders had water in them.The 327 has a forged crank and rods.But this is why I posted this question.Should I rebuild the 305?It will be more then the 327 and I think the 327 will take cruising at 5000 rpm.It already has forged crank forged pistons and the pink rods.But this is why I ask you guys.I can build a bullet proof race engine for a car but if you say rebuild the 305 I will go that rout.They are two different animals.Thanks Again guys.I need all the input I can get.

Re: mercruiser engine replacement

Leave it to ODDD1 to tell it like it is! When it comes to boating...there ain't nuttin' free! Amen to that!<br /><br />I repowered my trashed 305 with a new 350. Like Fouled Plug says...there's nothing like a wee more horsepower to change one's perspective...<br /><br />I'll echo the previous advice and also suggest you avoid taking any shortcuts...in other words, do it right. Good luck!<br /><br />Walt

Re: mercruiser engine replacement

The more I look the more I find.The engine in the boat according to the casting #s is a 305 used from80-85 with 2 bolt mains.According to mercs #s they used this engine from 83-84.I know that the 327 has a better bottom end then the 305 so Im going to have to use it with all forged parts Im sure it will take the abuse.Ill use everything else marine and pray.

Re: mercruiser engine replacement

Wheels, if you took that 305 apart, you would find a 2 bolt block, cast crank, standard production rods,and maybe even a nylon timing gear! The 305's did not get the real heavy duty stuff....although the upper end did have the better truck stuff....one caution about using that 327...make sure you have a mild enough cam in it to maintain a steady 750 max idle rpm...or you are gonna complain every time you try to shift it...